How to find and delete extra UV layers on many objects?
Script

Removes non active uv layers from all meshes in blend.  As with all scripts that remove things, save first.

import bpy

for me in bpy.data.meshes:
    uvs = [uv for uv in me.uv_layers 
            if uv !=  me.uv_layers.active]
    while uvs:
        me.uv_layers.remove(uvs.pop())


Removes all uv layers not marked active render.

import bpy

for me in bpy.data.meshes:
    uvs = [uv for uv in me.uv_layers
            if not uv.active_render]
    while uvs:
        me.uv_layers.remove(uvs.pop())